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While studying this effect in rats, Michael Bowen from the University of Sydney noticed something strange. Rats that had been given oxytocin didn’t seem to get drunk. “Those that had the oxytocin were up and moving about as if they hadn’t had any alcohol at all, whereas the ones that didn’t have oxytocin were quite heavily sedated,” Bowen says.

This effect was confirmed in a second experiment, in which half the rats were given an injection of oxytocin straight into the brain, at a level about 150,000 times what would normally be found there. They were then given alcohol, after which researchers tested their motor control and reaction times. Oxytocin seemed to completely counteract the effects of the booze – even when a rat had consumed what would be equivalent to about one and a half bottles of wine in humans. “The rats that had received oxytocin, as well as the alcohol, were virtually indistinguishable from the rats that hadn’t received any alcohol at all,” says Bowen.

This could be thanks to the brain’s GABA receptors, where alcohol is thought to exert its intoxicating effects. Bowen’s team found that oxytocin was binding to two parts of these receptors, blocking alcohol from getting there. “It was actually preventing alcohol affecting these sites in the brain that make you intoxicated.”

But the effect isn’t limitless. When the team gave some rats the equivalent of about a bottle of vodka, the oxytocin wasn’t enough to keep them awake. This is because at very high doses, alcohol starts to bind to GABA receptors that are inside neural connections, called synapses, where oxytocin can’t reach them.

Sobering up

“As exciting as it is to think this new application of oxytocin might allow people to have a few too many drinks at their lunchtime meeting and come back and be more productive in the afternoon, the significance does extend far beyond that,” says Bowen. The real promise of the finding is in treating alcohol-use disorders, he says. “While you might think that a drug that makes you feel less intoxicated might make you drink more, the opposite seems to be the case with oxytocin.”

“In addition to blocking alcohol intoxication, it has been shown that oxytocin reduces alcohol consumption, prevents the development of tolerance to alcohol and reduces the severity of alcohol withdrawal,” says Bowen.

“The effect is quite dramatic,” says Zoltan Sarnyai from James Cook University in Queensland, Australia. “If it holds up in humans, from a practical point of view, oxytocin could be an ideal drug.”

Bowen plans to investigate this use of oxytocin in humans soon, but because it is such a large molecule, it may be hard to get enough of it through the blood-brain barrier. However, he says that by finding which part of oxytocin binds to the GABA receptors, it should be possible to design smaller chemicals to do the same job.